Drying pad with polymer-agumented soil barrier

ABSTRACT

A drying pad and a method for constructing a drying pad for a wet waste, of which the method includes adding a polymer additive to a soil to create a polymer-augmented soil, and spreading the polymer-augmented soil over a base soil to create drying pad comprising a polymer-augmented soil layer on top of the base soil. The polymer-augmented soil is configured to have the wet waste deposited thereon so that the wet waste dries on top of the polymer-augmented soil layer without leaching into the base soil and produces a dried waste for transfer to a disposal cell. The method also includes removing the polymer-augmented soil layer from the base soil after the dried waste is transferred to the disposal cell.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/882,793, which was filed on Aug. 5, 2019 and is incorporatedherein by reference in its entirety.

BACKGROUND

Landfills typically have a pit or “cell” where solid waste is depositedfor permanent disposal. The waste that is deposited in such a cellgenerally has to pass a “paint filter” test, meaning that the wasteneeds to be solid enough in composition so that it does not permeatethrough filters such as those used to filter paint. By maintaining thatthe waste in the disposal cell has a certainly level of solidity, thewaste may not be prone to permeating through the barriers and linersmaintained at the boundaries of the cell. Nevertheless, disposal cellsgenerally include multiple, permanent layers of low-permeabilitymaterials to prevent waste from leaching out of the landfill into thesurrounding soil.

Often, at least some of waste that arrives at the landfill is toofluidic to pass the paint filter test. For example, in well-drillingapplications, cuttings that are separated from the mud, despite beingseparated, may still include too much hydrocarbon or other fluids toallow the cuttings to be placed directly into the disposal cell.Accordingly, a drying pad may be provided. In a drying pad, the wetwaste is spread out, open to the atmosphere and the sun, so it may dry.Dirt, sawdust, etc. may be added to the fluidic waste to further dry it.Thus, heavy equipment is often called for, which is used to spread thefluidic waste and mix in the drying additives. The drying pads can bequite large (e.g., acres), and generally are required to have a very lowpermeability, given the fluidic-waste application and the desire toavoid such waste fluid leaching into the soil around the drying pad.Accordingly, an impermeable membrane, typically a compacted clay layeror geosynthetic clay liner are used to prevent any fluids frompermeating the soil beneath the drying pad.

As mentioned above, however, heavy equipment is used on the drying padto work and move the material. To avoid this equipment damaging therelatively fragile liners and/or compacted clay, several feet of soilcan be placed on top of the clay and liner. This design works well andis generally the standard in the industry for drying pads. However,despite the presence of the sacrificial soil layer, the liner and/orclay beneath is eventually damaged during the life of the drying pad.Thus, continual maintenance, and the time, energy, and expenseassociated therewith, is required to keep the drying pads working toprevent leachate.

SUMMARY

Embodiments of the disclosure provide a method for constructing a dryingpad for a wet waste. The method includes adding a polymer additive to asoil to create a polymer-augmented soil, and spreading thepolymer-augmented soil over a base soil to create drying pad comprisinga polymer-augmented soil layer on top of the base soil. Thepolymer-augmented soil is configured to have the wet waste depositedthereon so that the wet waste dries on top of the polymer-augmented soillayer without leaching into the base soil and produces a dried waste fortransfer to a disposal cell. The method also includes removing thepolymer-augmented soil layer from the base soil after the dried waste istransferred to the disposal cell.

Embodiments of the disclosure further provide a drying pad for alandfill. The drying pad includes a base soil layer, and apolymer-augmented soil layer disposed on top of the base soil layer,wherein the polymer-augmented soil layer includes a polymer additive,and is harder and less permeable than the base soil layer.

Embodiments of the disclosure also provide a method for drying a wetwaste in preparation for disposal in a landfill. The method includesselecting an area proximal to a disposal cell for a drying pad,loosening a layer of soil in the area selected for the drying pad,adding a polymer additive to the loosened soil to create apolymer-augmented soil, spreading and compacting the polymer-augmentedsoil on a base soil to create a polymer-augmented soil layer, curing thepolymer-augmented soil layer, depositing the wet waste directly on thecured polymer-augmented soil layer so that the wet waste dries on top ofthe polymer-augmented soil layer and produces a dried waste, after thewet waste dries to produce the dried waste, transferring the dried wasteto the disposal cell, removing the polymer-augmented soil layer from thebase soil after transferring the dried waste to the disposal cell, andtransferring the polymer-augmented soil layer to the disposal cell afterremoving the polymer-augmented soil layer from the base soil.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure may best be understood by referring to thefollowing description and accompanying drawings that are used toillustrate embodiments of the invention. In the drawings:

FIG. 1 illustrates a plan view of a landfill site including a dryingpad, according to an embodiment.

FIG. 2 illustrates a cross-sectional view of the drying pad, accordingto an embodiment.

FIG. 3 illustrates a flowchart of a method for constructing a drying padand disposing of a wet waste, according to an embodiment.

DETAILED DESCRIPTION

The following disclosure describes several embodiments for implementingdifferent features, structures, or functions of the invention.Embodiments of components, arrangements, and configurations aredescribed below to simplify the present disclosure; however, theseembodiments are provided merely as examples and are not intended tolimit the scope of the invention. Additionally, the present disclosuremay repeat reference characters (e.g., numerals) and/or letters in thevarious embodiments and across the Figures provided herein. Thisrepetition is for the purpose of simplicity and clarity and does not initself dictate a relationship between the various embodiments and/orconfigurations discussed in the Figures. Moreover, the formation of afirst feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed interposing the first and secondfeatures, such that the first and second features may not be in directcontact. The embodiments presented below may be combined in anycombination of ways, e.g., any element from one exemplary embodiment maybe used in any other exemplary embodiment, without departing from thescope of the disclosure.

Additionally, certain terms are used throughout the followingdescription and claims to refer to particular components. As one skilledin the art will appreciate, various entities may refer to the samecomponent by different names, and as such, the naming convention for theelements described herein is not intended to limit the scope of theinvention, unless otherwise specifically defined herein. Further, thenaming convention used herein is not intended to distinguish betweencomponents that differ in name but not function. Additionally, in thefollowing discussion and in the claims, the terms “including” and“comprising” are used in an open-ended fashion, and thus should beinterpreted to mean “including, but not limited to.” All numericalvalues in this disclosure may be exact or approximate values unlessotherwise specifically stated. Accordingly, various embodiments of thedisclosure may deviate from the numbers, values, and ranges disclosedherein without departing from the intended scope. Finally, unlessotherwise provided herein, “or” statements are intended to benon-exclusive; for example, the statement “A or B” should be consideredto mean “A, B, or both A and B.”

FIG. 1 illustrates a plan view of a landfill site 100, according to anembodiment. The landfill site 100 may include a disposal cell 102 and adrying pad 104. The disposal cell 102 may be a pit, which may have oneor more layers of compacted soil, geosynthetic textiles, plastic liners(HDPE), and/or the like. The disposal cell 102 may be configured forpermanently receiving relatively solid (dry) waste. The disposal cell102 is permanent in contrast to the drying pad 104, as described herein.

The drying pad 104 may be positioned near the disposal cell 102, e.g.,adjacent thereto, as shown. The drying pad 104 may be configured toreceive relatively fluidic (wet) waste 110, and may allow the waste tobe exposed to the atmosphere, the sun, etc., e.g., by providing arelatively impermeable area for the wet waste to be spread out. Once thewet waste is dried or solidified, the waste may be transferred to thedisposal cell 102 for permanent disposal. In other words, the waste 110is temporarily placed on the drying pad 104.

FIG. 2 illustrates a cross-sectional view of the drying pad 104,according to an embodiment. The drying pad 104 may include a base layerof soil 200 and a polymer-augmented soil layer 202 positioned verticallyabove the base layer of soil 200. The waste 110 is deposited on top ofthe polymer-augmented soil layer 202. To create this cross-section, thedrying pad 104 may begin as solely the base layer of soil 200. Watermixed with polymer additive is then added to the base layer of soil 200to stabilize and compact at least a portion of the base layer of soil200. This, in addition to the curing of the polymer additive, results inthe polymer-augmented soil layer 202. To name one specific example, thepolymer additive may be, for example, TOP SEAL WHITE™, which iscommercially available from ENVIROTX.

The polymer additive may change the characteristics of the soil, suchthat the soil layer 202 is less permeable and harder than the base layer200. For example, once the polymer additive is mixed in and cured, theaugmented soil layer 202 may have a permeability of between about 1×10⁻⁹cm/s and about 1×10⁻⁷ cm/s. Further, the hardness of the soil layer 202may be between about 400 psi and about 800 psi, e.g., about 600 psi, orgreater. The soil layer 202 may have a thickness of between about 4inches and about 12 inches, e.g., about 8 inches. Thus, the soil layer202 may be substantially harder than compacted clay or traditionalliners, but not as hard (or expensive) as, for example, concrete. Assuch, the soil 202 may be able to directly receive the wet waste and maysupport the heavy earth-moving equipment that is used to work the wetwaste, while resisting damage as compared to clay or liners. Thus, insome embodiments, another layer of sacrificial soil may not need to beplaced on top of the polymer-augmented soil layer 202, but in otherembodiments, such a sacrificial soil layer may be used.

FIG. 3 illustrates a flowchart of a method 300 for constructing a dryingpad 104 and drying a wet waste on the drying pad 104, according to anembodiment. The method 300 may include selecting an area proximal to adisposal cell 102 for the drying pad 104, as at 302. As shown in FIG. 1,the disposal cell 102 and the drying pad 104 may be immediately adjacentto one another, but they could be farther part or in different relativeorientations, have different shapes, etc.

The method 300 may also include determining an amount of polymeradditive and a polymer-augmented soil layer depth for the drying pad104, as at 304. For example, the polymer-augmented soil layer may, e.g.,to comply with regulatory requirements, be designed to have a specificpermeability and/or specific hardness, e.g., in the ranges noted above.These characteristics may be at least partially based on the compositionof the soil, prior to application of the polymer additive, which mayimpact the amount of polymer additive and the depth of thepolymer-augmented soil layer. For example, soil that is more uniformlysized (“well graded”) may require more polymer additive and/or a thickerlayer. Soil that is less uniformly sized (“poorly graded”) may requireless polymer additive and/or a thinner layer, by comparison.Accordingly, determining at 304 may include taking soil samples todetermine soil properties, which in turn are used to determine an amountof polymer additive to add and a thickness/depth for thepolymer-augmented soil layer.

The method 300 may also include loosening (tilling) a layer of soil inthe area that was selected, as at 306. The area may have a base soil,which may extend a depth that exceeds the depth that is loosened.Accordingly, the loosened soil and the base soil may, initially, be ofthe same general composition, e.g., including the same amounts of sand,gravel, clay, etc., to the extent the base soil is generally of ahomogenous composition itself. The soil may be loosened usingearth-moving equipment, and the area that was selected may be an acre ormore in size.

Once the soil is loosened, the polymer additive may be added to theloosened soil, as at 308. This may be accomplished by mixing the polymeradditive with a solvent (e.g., water). The soil may then be “worked”(e.g., moved around by the earth moving equipment) to mix the polymeradditive with the soil, thereby producing a polymer-augmented soil thathas generally a consistent amount of polymer additive throughout.

The polymer-augmented soil may then be spread and/or compacted on thebase soil in the area, as at 310. As such, a layer of polymer-augmentedsoil is created (e.g., layer 202 on top of base soil 200 in FIG. 2). Thepolymer-augmented soil layer may be formed directly on the base layer,with no intervening layers such as clay, geosynthetic textiles, etc.,therebetween. Further, there may be no such layers on top of thepolymer-augmented soil layer either, nor a layer of “sacrificial” soil,such as those often used to protect liners, geosynthetic materials.,etc. from damage. The polymer-augmented soil layer may then be allowedto cure, resulting in a layer that has the thickness and permeabilitydetermined at 304. At this point, the drying pad 104 is ready to acceptwet waste for drying.

Accordingly, the wet waste for disposal may then be deposited on thepolymer-augmented soil layer, as at 312. The wet waste may then beallowed to dry, as at 314, which may include passively waiting forevaporation and/or actively adding materials, such as sawdust, to thewet waste, as described above. Wet waste is defined as waste that is toofluidic to pass the paint filter test. By contrast, after drying the wetwaste, a dried waste is produced. Dried waste is defined as waste thatdoes pass the paint filter test, although it may still be somewhatfluidic in consistency or appearance.

The dried waste may then be transferred into the disposal cell 102, asat 316. In contrast to the drying pad 104, the disposal cell 102 ispermanent and includes potentially several low-permeability layersconfigured to confine the contents of the disposal cell 102indefinitely.

At some point, the usefulness of the drying pad 104 reaches an end,e.g., when the disposal cell 102 is full, or when no further wet wasteis to be received. At this point, the drying pad 104 may be removed. Toremove the drying pad 104, the method 300 includes removing thepolymer-augmented soil layer, as at 318. This may include again usingthe earth-moving equipment to dig up the polymer-augmented soil layerand expose the base soil. The removed polymer-augmented soil layer maythen be transferred into the disposal cell 102, as at 320.

The foregoing has outlined features of several embodiments so that thoseskilled in the art may better understand the present disclosure. Thoseskilled in the art should appreciate that they may readily use thepresent disclosure as a basis for designing or modifying other processesand structures for carrying out the same purposes and/or achieving thesame advantages of the embodiments introduced herein. Those skilled inthe art should also realize that such equivalent constructions do notdepart from the spirit and scope of the present disclosure, and thatthey may make various changes, substitutions, and alterations hereinwithout departing from the spirit and scope of the present disclosure.

What is claimed is:
 1. A method for constructing a drying pad for a wetwaste, the method comprising: adding a polymer additive to a soil tocreate a polymer-augmented soil; spreading the polymer-augmented soilover a base soil to create drying pad comprising a polymer-augmentedsoil layer on top of the base soil, wherein the polymer-augmented soilis configured to have the wet waste deposited thereon so that the wetwaste dries on top of the polymer-augmented soil layer without leachinginto the base soil and produces a dried waste for transfer to a disposalcell; and removing the polymer-augmented soil layer from the base soilafter the dried waste is transferred to the disposal cell.
 2. The methodof claim 1, further comprising: selecting an area proximal to thedisposal cell for the drying pad; and loosening a layer of soil in thearea selected for the drying pad, wherein the polymer additive is addedto the loosened layer of soil in the area to create the drying pad, andwherein the wet waste is deposited in the area of the drying pad.
 3. Themethod of claim 2, wherein the area of the drying pad is at least oneacre in size.
 4. The method of claim 1, wherein the polymer-augmentedsoil is spread directly on the base soil, and wherein thepolymer-augmented soil is harder and less permeable than the base soil.5. The method of claim 1, wherein loosening the layer of soil comprisestilling the base soil using earth-moving equipment.
 6. The method ofclaim 1, further comprising transferring the polymer-augmented soillayer to the disposal cell after removing the polymer-augmented soillayer.
 7. The method of claim 1, wherein adding the polymer additive tothe soil comprises spreading a mixture of the polymer additive and asolvent on the soil, and working the polymer additive into the soilusing ground-moving equipment.
 8. The method of claim 1, whereindepositing the wet waste on the polymer-augmented soil layer comprisesdepositing the wet waste directly on the polymer-augmented soil layer,without any other layers of soil, clay, or geosynthetic materialstherebetween.
 9. The method of claim 1, further comprising: sampling thesoil prior to adding the polymer additive; and determining a depth forthe polymer-augmented soil layer and amount of polymer additive to addto the soil to reach a predetermined permeability for the layer, basedin part on the sampled soil.
 10. The method of claim 9, wherein thepredetermined permeability is about 1×10⁻⁷ cm/s.
 11. The method of claim9, wherein determining the depth and the amount of polymer additivefurther comprises determining the amount of polymer additive to add toreach a predetermined hardness for the layer of soil.
 12. The method ofclaim 11, wherein the predetermined hardness is about 600 psi.
 13. Adrying pad for a landfill, comprising: a base soil layer; and apolymer-augmented soil layer disposed on top of the base soil layer,wherein the polymer-augmented soil layer includes a polymer additive,and is harder and less permeable than the base soil layer.
 14. Thedrying pad of claim 13, wherein the polymer-augmented soil layer isconfigured to receive a wet waste directly thereon.
 15. The drying padof claim 14, wherein the polymer-augmented soil layer is configured tobe removed after the wet waste is dried thereon.
 16. The drying pad ofclaim 15, wherein the drying pad does not include a sacrificial soillayer positioned between the wet waste and the polymer-augmented soillayer.
 17. The drying pad of claim 13, wherein the polymer-augmentedsoil layer has a hardness of about 600 psi.
 18. The drying pad of claim13, wherein the polymer-augmented soil layer has a permeability of atmost about 1×10⁻⁷ cm/s.
 19. A method for drying a wet waste inpreparation for disposal in a landfill, the method comprising: selectingan area proximal to a disposal cell for a drying pad; loosening a layerof soil in the area selected for the drying pad; adding a polymeradditive to the loosened soil to create a polymer-augmented soil;spreading and compacting the polymer-augmented soil on a base soil tocreate a polymer-augmented soil layer; curing the polymer-augmented soillayer; depositing the wet waste directly on the cured polymer-augmentedsoil layer so that the wet waste dries on top of the polymer-augmentedsoil layer and produces a dried waste; after the wet waste dries toproduce the dried waste, transferring the dried waste to the disposalcell; removing the polymer-augmented soil layer from the base soil aftertransferring the dried waste to the disposal cell; and transferring thepolymer-augmented soil layer to the disposal cell after removing thepolymer-augmented soil layer from the base soil.
 20. The method of claim19, wherein: the area of the drying pad is at least one acre in size;and the polymer-augmented soil is positioned directly on the base soilto form the polymer-augmented soil layer, and wherein thepolymer-augmented soil layer is harder and less permeable than the basesoil, the polymer-augmented soil having g a hardness of between about600 psi and about 1000 psi and a permeability of between about 1×10⁻⁸cm/s and about 1×10⁻⁷ cm/s.